The importance of a good overhang!

In Wales we have had a tendency to design our houses with the minimal amount of overhang on the roof. The tiles sit very close to the walls. This has meant that anything else that we add to the depth of the walls loses precious protection for the wall plate. So rendering and over cladding often has the unintended consequence of making the inner wall more liable to water ingress. Where the over cladding is water proof this can easily trap wind driven rain / overflow from blocked guttering into the structure.

I was in a house last week where the fascias have been twisted and are now potentially channelling water into the building. Another building around the corner from the centre is also suffering after the owners installed external wall insulation. Here the builders had put one of those awful plastic covers over the top of the insulation to 'provide protection' against rain. Surprise, surprise a few months later they were back extending the roof to do the job properly! Wind and rain are a potent force in Wales!

The junction between roof and wall is one of the weakest in a house and so we must be very strict about how we protect walls from the elements. Extending the roof line may seem like a costly addition to any work on the external walls, but if you are doing work on them it may actually save you money if you get it done at the same time. Certainly it would have saved the people around the corner a pretty packet on their scaffolding costs!

If you look at houses on the continent, most have large roof overhangs. This helps to protect the building fabric, provides shading against the summer sun (and with climate change we might even get some of this at some point!), gives additional shelter for windows etc. Learning a lesson or two from the near continent is always a good idea.

Note: this post was first published in 2013. Check through our whole blog for other interesting articles.

Shoe missing in street

This could be titled: 'How to get a roof load of water into your floors and walls'.

Note the crack between the wall and the pavement

This is a very common sight in urban areas. Downpipes have had their shoes kicked off / removed and so all the water from the roof is being poured into the base of the wall rather than angled off into the main road drain.

In this particular location there was a large gap between the council's pavement and the wall. This has meant that for years the wall have been subjected to way more rainwater than it can cope with. No wonder there was damp in the wall inside.

The simple solution is to re-fit the shoe and get the system back working again. There will still be runoff entering the gap, but at least the volumes might decrease to a level where the wall can cope again.

Oh, for those who were wondering a 'shoe' is as follows:

Cement render = Rotten wood

Removing render exposes timber issues under cracks

One of the other issues that the removal of the cement render exposed was the condition of the wood in the structure.

Admittedly the house has a strange array of wood that has appeared in the most unusual places - joists that go all the way through the house from external surface to external surface. The trouble is that this change in underlying surface meant that the cement render was more likely to crack here. Of course, being cement, it did and this in turn allowed water to get behind the render. This concentration in damp behind the cement of course then fed into the wood.

This is one of the big concerns with cement rendering old houses as it it not obvious until it eventually gives way. One of the many problems that we are storing up for the future generations, by not understanding older properties well enough.

So, if you do have a solid walled house make sure that you maintain any render really well - remove cracks when they form etc. If you do get around to needing to re-render, then do so using a lime based render but also expect to un-earth a range of problems.

I feel that this is a similar situation to the climate change arguments. It is out of sight and so out of mind. It is also largely controlled by large companies with vested interests and so they will not lead the way for change as their industry is profitable as it stands, so why rock the boat, even if you know what you are supplying is ruining the environment (the built one that is rather than the natural one).

Damp appearing?

In this sort of weather you might find damp in places that were dry before. Why?

Well, when you have driving rain rather than just rain it tends to get into cracks and holes that it might otherwise miss. Key areas that are at risk are:

1. Silicone seals around doors and windows - the sealant fails over time and comes away from the wall or frame, this then allows water to get driven in behind. When the wall gets wet it transmits heat better and so it gets colder. The cold patch then attracts condensation, this then leads to mould formation etc. Builders and DIY'ers are quite notorious for choosing the cheapest / most obvious option. These silicons are the most likely to fail, because basically they are rubbish. Look for a more elastic silicon and one that will adhere for longer. They will all eventually fail, but putting more time between replacement is just easier.

2. Poor pointing - pointing is really important for keeping out driving rain. It can fail in a number of ways. Firstly it can be re-pointed using the wrong mortar. Using cement on old solid walls is fundamentally wrong. It traps water in and also ruins the softer brick / stone. Always use a lime mortar (preferably lime putty with stone dust). Rake out to a depth that is double the height, get it wet first and then press the mortar well into the joints. Pointing should be flush with the bricks / stone.

3. Cracks in render - in a similar vein to the pointing, render on older buildings should be lime based not cement. Again wind driven rain gets into the thinnest cracks and gets stuck behind the cement render. Ideally any cement render should be removed, but at the very least cracks should be repaired to stop the water ingress.

4. Leaky gutters - I see no end of leaky gutters at this time of the year. This is because we use poor quality, narrow plastic guttering, downpipes and fixings. The ideal is to use the correctly sized metal guttering (like Lindab), but at the very least make sure that your guttering is not leaking and draining correctly. Water flowing over walls and behind fascias is asking for trouble.

The main message is MAINTENANCE. Whatever you have on your house just make sure that it is working as well as it can. Then, if possible, look for more permanent solutions in the Spring / Summer when the rain stops!!!!! Lime, especially is easier to apply when it is drier and warmer, so good lime contractors are at a premium during this time, so get in quick.